Now showing 1 - 10 of 16
  • Publication
    The Role of Ionic Liquids in Performance Enhancement of Two‐Step Perovskite Photovoltaics
    (2023)
    Liang, Xiao
    ;
    Duan, Dawei
    ;
    Al-Handawi, Marieh B.
    ;
    Wang, Fei
    ;
    Zhou, Xianfang
    ;
    Ge, Chuang-ye
    ;
    Lin, Haoran
    ;
    Quanyao Zhu
    ;
    ;
    Naumov, Panče
    ;
    Hu, Hanlin
    Much of the research efforts of late that are directed toward enhancement of the efficiency of perovskite-based photovoltaics are focused on the application of ionic liquids (ILs) in a one-step approach. On the contrary, the details of the alternative two-step approach, such as the role of the ILs in the perovskite film solidification and its optoelectronic properties, remain poorly understood despite the increasing evidence that this latter method might offer considerable advantages, including better reproducibility and control over crystallization. Herein, the effect of IL methylammonium acetate (MAAc) introduced into the PbI2 layer by a sequential deposition process on the optoelectronic properties of the perovskite film and the performance of the ensuing photovoltaic devices are studied. The addition of MAAc lowers the MAAc–perovskite formation enthalpy, leading to an accelerated solidification process. Moreover, MAAc suppresses the formation of Pb0, thereby facilitating the perovskite formation while lowering the deep defect states caused by Pb0. In addition to grain boundary passivation, the acetate ions can diffuse into the bulk of the perovskite material, filling up the halide vacancies with reduced trap state density. As a result, a decent power conversion efficiency of 23.36% is achieved, with noticeably improved durability.
      16
  • Publication
    Autonomous and directional flow of water and transport of particles across a subliming dynamic crystal surface
    (2023)
    Commins, Patrick
    ;
    Al-Handawi, Marieh B.
    ;
    Rezgui, Rachid
    ;
    ;
    McNamara, Mark
    ;
    Naumov, Panče
    Chemical and morphological traits of natural substrates that can propel and transport fluids over their surfaces have long provided inspiration for the engineering of artificial materials that can harvest and collect water from aerial humidity. Here we report that the gradual widening of parallel microchannels on a surface of a slowly subliming hexachlorobenzene crystal can promote the autonomous and bidirectional transduction of condensed aerial water. Driven by topology changes on the surface of the crystal and water exchange with the gas phase, droplets of condensed water migrate over the crystal. These droplets are also able to transport silver particles and other particulate matter, such as dust. The velocity of the particles was shown to be dependent on both the sublimation rate of the crystal and the relative humidity of its environment. This example of a sublimation-powered water flow demonstrates that topological surface changes accompanying crystal phase transitions can be harnessed to transport liquid and solid matter over surfaces.
      10
  • Publication
    Bioinspired soft robots based on organic polymer-crystal hybrid materials with response to temperature and humidity
    (2023)
    Yang, Xuesong
    ;
    Lan, Linfeng
    ;
    Pan, Xiuhong
    ;
    Di, Qi
    ;
    Liu, Xiaokong
    ;
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    The capability of stimulated response by mechanical deformation to induce motion or actuation is the foundation of lightweight organic, dynamic materials for designing light and soft robots. Various biomimetic soft robots are constructed to demonstrate the vast versatility of responses and flexibility in shape-shifting. We now report that the integration of organic molecular crystals and polymers brings about synergistic improvement in the performance of both materials as a hybrid materials class, with the polymers adding hygroresponsive and thermally responsive functionalities to the crystals. The resulting hybrid dynamic elements respond within milliseconds, which represents several orders of magnitude of improvement in the time response relative to some other type of common actuators. Combining molecular crystals with polymers brings crystals as largely overlooked materials much closer to specific applications in soft (micro)robotics and related fields.
      28
  • Publication
    Collective photothermal bending of flexible organic crystals modified with MXene-polymer multilayers as optical waveguide arrays
    (2023)
    Yang, Xuesong
    ;
    Lan, Linfeng
    ;
    ;
    Yu, Jinyang
    ;
    Liu, Xiaokong
    ;
    Tao, Ying
    ;
    Yang, Quan-Hong
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    The performance of any engineering material is naturally limited by its structure, and while each material suffers from one or multiple shortcomings when considered for a particular application, these can be potentially circumvented by hybridization with other materials. By combining organic crystals with MXenes as thermal absorbers and charged polymers as adhesive counter-ionic components, we propose a simple access to flexible hybrid organic crystal materials that have the ability to mechanically respond to infrared light. The ensuing hybrid organic crystals are durable, respond fast, and can be cycled between straight and deformed state repeatedly without fatigue. The point of flexure and the curvature of the crystals can be precisely controlled by modulating the position, duration, and power of thermal excitation, and this control can be extended from individual hybrid crystals to motion of ordered two-dimensional arrays of such crystals. We also demonstrate that excitation can be achieved over very long distances (>3 m). The ability to control the shape with infrared light adds to the versatility in the anticipated applications of organic crystals, most immediately in their application as thermally controllable flexible optical waveguides for signal transmission in flexible organic electronics.
      2
  • Publication
    Repair and Splicing of Centimeter‐Size Organic Crystalline Optical Waveguides
    (2023)
    Lan, Linfeng
    ;
    ;
    Yang, Xuesong
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Organic single crystals that are capable of transmitting light and charge are quickly shaping into a new forefront of research in photoelectronic materials that is thought to hold a tremendous potential for the broader field of organic electronics. However, one of the main disadvantages that currently stands against the direct application of organic single crystals in that capacity is their pronounced proneness to mechanical damage due to brittleness, abrasion, and wear. To account for this drawback, here a simple and universal strategy is proposed for the recovery of macroscopic integrity of cracked or completely fractured crystals based on the layer-by-layer charged polymer assembly approach that can be used to effectively recover the damaged crystals. It is shown that in addition to being an effective means for reasonable restoration of their optical waveguiding ability, this approach can also be used to combine different crystals into hybrid organic photonic integrated circuits (OPICs) and even to construct dynamic hybrid OPICs as active and/or passive optical waveguides. The resulting integrated crystalline OPIC bundles act as optical waveguides for transmission of light with different colors and can also be used for light mixing to generate white light.
      6
  • Publication
    Elastic Organic Crystals as Bioinspired Hair‐Like Sensors
    (2023)
    Yousuf, Soha
    ;
    Halabi, Jad Mahmoud
    ;
    Tahir, Ibrahim
    ;
    Ahmed, Ejaz
    ;
    Rezgui, Rachid
    ;
    ;
    Laws, Praveen
    ;
    Daqaq, Mohammed
    ;
    Naumov, Panče
    One of the typical haptic elements are natural hairy structures that animals and plants rely on for feedback. Although these hair sensors are an admirable inspiration, the development of active flow sensing components having low elastic moduli and high aspect ratios remains a challenge. Here, we report a new sensing approach based on a flexible, thin and optically transmissive organic crystal of high aspect ratio, which is stamped with fluorescent dye for tracking. When subjected to gas flow and exposed to laser, the crystal bends due to exerted pressure and acts as an optical flow (hair) sensor with low detection limit (≈1.578 m s−1) and fast response time (≈2.70 s). The air-flow-induced crystal deformation and flow dynamics response are modelled by finite element analysis. Due to having a simple design and being lightweight and mechanically robust this prototypical crystal hair-like sensor opens prospects for a new class of sensing devices ranging from wearable electronics to aeronautics.
      7Scopus© Citations 1
  • Publication
    Exceptionally high work density of a ferroelectric dynamic organic crystal around room temperature
    (2022) ;
    Karothu, Durga Prasad
    ;
    Ferreira, Rodrigo
    ;
    Dushaq, Ghada
    ;
    Ahmed, Ejaz
    ;
    Catalano, Luca
    ;
    Halabi, Jad Mahmoud
    ;
    Alhaddad, Zainab
    ;
    Tahir, Ibrahim
    ;
    Mohamed, Sharmarke
    ;
    Rasras, Mahmoud
    ;
    Naumov, Panče
    Dynamic organic crystals are rapidly gaining traction as a new class of smart materials for energy conversion, however, they are only capable of very small strokes (<12%) and most of them operate through energetically cost-prohibitive processes at high temperatures. We report on the exceptional performance of an organic actuating material with exceedingly large stroke that can reversibly convert energy into work around room temperature. When transitioning at 295–305 K on heating and at 265–275 K on cooling the ferroelectric crystals of guanidinium nitrate exert a linear stroke of 51%, the highest value observed with a reversible operation of an organic single crystal actuator. Their maximum force density is higher than electric cylinders, ceramic piezoactuators, and electrostatic actuators, and their work capacity is close to that of thermal actuators. This work demonstrates the hitherto untapped potential of ionic organic crystals for applications such as light-weight capacitors, dielectrics, ferroelectric tunnel junctions, and thermistors.
      19
  • Publication
    Organic Crystalline Optical Waveguides That Remain Elastic from -196 to ≈ 200°C
    (2022) ;
    Tang, Shiyue
    ;
    Ye, Kaiqi
    ;
    Commins, Patrick
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Organic crystals that are capable to deform (reversibly or irreversibly) similar to polymer materials have been widely reported over the past ten years. However, most of the reported organic crystals can only be elastically bent within a narrow temperature range, and reports on their thermal behavior that would encourage applications of these energy-transducing elements in extreme conditions are not readily available. This work designs a linear and flat π-conjugated molecule with double intramolecular hydrogen bonds that prevent thermally induced conformational distortions. The molecule assembles as a rigid building block into centimeter-sized wide organic crystals that can be elastically bent over a temperature range spanning close to 400 °C, from −196 to ≈200 °C. The emission wavelength of the crystals is also temperature dependent, and can be continually tuned from 547 to 577 nm upon heating from 20 to ≈200 °C. This inspires the design of a lightweight, organic, elastic optical waveguide where the output energy is controlled by the operating temperature. The wide range of crystal flexibility expands the range of conditions for application of organic crystals as optical waveguides.
      17
  • Publication
    Recent Progress in Ionic Liquids for Stability Engineering of Perovskite Solar Cells
    (2022) ;
    Wang, Fei
    ;
    Ge, Chuang-ye
    ;
    Duan, Dawei
    ;
    Lin, Haoran
    ;
    Naumov, Panče
    ;
    Hu, Hanlin
    Perovskite solar cells attract widespread attention due to their impressive power conversion efficiencies, high absorption coefficients, tunable bandgap, and straightforward manufacturing protocols. However, in the process of further development and optimization toward mass production, the long-term stability stands as one of the most urgent challenges that need to be overcome. Given the excellent thermal stability and high structural designability, ionic liquids (ILs) are relatively green room-temperature molten salts that have been widely applied to perovskite photovoltaic devices with promising results in view of improved stability and enhanced device performance. In this review, the reasons and mechanisms of instability of such devices under external and internal factors are analyzed. The current strategies of ILs engineering for improved stability of the devices are classified and summarized, including the IL-assisted perovskite film evolution and IL-modified photophysical properties of the perovskite photoactive layer and the related stability and photovoltaic performance of the devices. The challenges that stand as obstacles toward further development of perovskite solar cells based on IL engineering and their prospects are also discussed.
      17  21
  • Publication
    Remote and precise control over morphology and motion of organic crystals by using magnetic field
    (2022) ;
    Yang, Xuesong
    ;
    Lan, Linfeng
    ;
    Liu, Xiaokong
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Elastic organic crystals are the materials foundation of future lightweight flexible electronic, optical and sensing devices, yet precise control over their deformation has not been accomplished. Here, we report a general non-destructive approach to remote bending of organic crystals. Flexible organic crystals are coupled to magnetic nanoparticles to prepare hybrid actuating elements whose shape can be arbitrarily and precisely controlled simply by using magnetic field. The crystals are mechanically and chemically robust, and can be flexed precisely to a predetermined curvature with complete retention of their macroscopic integrity at least several thousand times in contactless mode, in air or in a liquid medium. These crystals are used as optical waveguides whose light output can be precisely and remotely controlled by using a permanent magnet. This approach expands the range of applications of flexible organic crystals beyond the known limitations with other methods for control of their shape, and opens prospects for their direct implementation in flexible devices such as sensors, emitters, and other (opto)electronics.
    Scopus© Citations 20  28  27